Progesterone enhances reactive oxygen intermediates production by cultured human monocytes.

Progesterone at placental tissue concentrations (5-20 micrograms/ml) markedly increases in vitro PMA-stimulated O-2 and H2O2 production by human cultured monocytes. This appears to contrast the well-known suppressive action of the hormone on the other cell mediated defence mechanisms. We suggest that these findings could cast a new light on progesterone's multiple and differentiated functions in the placental environment.